1. Field
The disclosed subject matter relates to a projector-type lighting device such as a headlight for a vehicle, and in particular, relates to a headlight which can provide a plurality of light distribution patterns including a passing-by light distribution pattern (or a low-beam light distribution), a traveling light distribution pattern (or a high-beam light distribution), and the like.
2. Brief Description of the Related Art
FIG. 1 shows a conventional projector-type headlight 90 which can selectively provide a low-beam light distribution pattern and a high-beam light distribution pattern. The projector-type headlight 90 has a lighting body 91, an ellipsoidal reflector 95, and a horizontal shaft 92 which is located near the second focus F2 of the ellipsoidal reflector 95 and extends in the widthwise direction of the vehicle. Light shielding plates 93L and 93R are attached to the horizontal shaft 92.
The light shielding plate 93L projects from the horizontal shaft 92 to an appropriate extent so as to form a low-beam light distribution pattern for the keep-to-the-left traffic system, and for emitting appropriate upward light beams to the left side. The light shielding plate 93R also projects from the horizontal shaft 92 to an appropriate extent so as to form a low-beam light distribution pattern for the keep-to-the-right traffic system, and for emitting appropriate upward light beams to the right side.
In this instance, both the light shielding plates 93L and 93R are located without interfering with the light reflected from the upper half 95U of the ellipsoidal reflector 95. For example, when the light shielding plate 93L is inserted in the light path for the light reflected from the upper half 95U to form a required light distribution pattern, the other light shielding plate 93R is configured not to function.
Between the light shielding plates 93L and 93R, a recessed portion 94 is arranged for allowing a part of the light reflected from the lower half 95D of the ellipsoidal reflector 95 to pass therethrough.
When the horizontal shaft 92 thus configured is rotated by an appropriate driving means such as a stepping motor, for example, each of the light shielding plates 93L and 93R can be positioned at a corresponding position, thereby providing a required low-beam light distribution pattern. It should be noted that the reference numeral 96 in this figure denotes a projection lens for projecting light with a required light distribution pattern formed by the light shielding plate 93L or 93R. (See Japanese Patent Laid-Open Publication No. 2004-349120 and U.S. Pat. No. 7,090,385 the disclosure of which is hereby incorporated in its entirety by reference).
In recent years, vehicle headlights may be provided with a so-called town driving light distribution pattern including no upward light irrespective of the keep-to-the-left or right traffic system. This town driving light distribution pattern may be adopted to a vehicle with an AFS system which can change its headlight direction along with steering and possibly other operations.
When each of the light shielding plates 93L and 93R of the projector-type headlight 90 is set to be located at a predetermined position, the specified corresponding light distribution pattern can be obtained. However, the headlight 90 with this configuration has the rotated horizontal shaft 92 arranged perpendicularly to the illumination direction. Therefore, when the positional relationship between the light shielding plates 93L and 93R is changed to switch the light distribution pattern, the transition light distribution pattern is significantly varied instantaneously and for a period of time (for example, for approximately 0.3 seconds). That is, during the switching operation, part of light is incident on, for example, the horizontal shaft 92 and is reflected and directed in unexpected directions. This reflected light may be emitted through the projection lens 96 to the outside.
In this case, the transition light distribution pattern is undesirably varied from the required light distribution pattern in accordance with its specification although the light is emitted for a short period of time. This light may become glaring light that is incident on opposing vehicles, pedestrians, etc. Therefore, this transition light distribution pattern should be improved. In particular, there is a long felt need for this problem to be solved in view of the increasing number of vehicles adopting AFS systems.